Monitor problems

[rigeback]

Re: Monitor problems

Part number for U-6 = NA2X
What is the LDO regulator and how bad is the problem? Let me know if you think I should scrap it!

[momaka]

Re: Monitor problems

Part number for U-6 = NA2X

Can't seem to find a datasheet for it. From the connections on its legs, though, it seems like a Feeling Technology FP5138, which is a boost controller IC. I have seen it used on a few other monitors, so this is likely it.

What is the LDO regulator and how bad is the problem?

LDO stands for Low Drop-Out. U1 is a LDO voltage regulator - it takes some voltage and outputs a lower, regulated, voltage that may then be used by some logic chip or whatever else.
The part numbers on U1 will allow me to see what voltage U1 should be outputting so I can see weather or not it's bad.

Also, I just noticed that U4 has some kind of discoloration or dark spot on it. Not sure if it's from the picture or not. Can you verify what it is?

Let me know if you think I should scrap it!

Well, that's up to you really. Usually it's not economical to fix such issues as a bad t-con - not unless it's something really simple. So if you fix LCD monitors for a living, then fixing this issue would not be worthwhile.
However, if you're trying to fix this monitor just for fun or for a learning experience, then you should keep it and try a few more things.

My advice is to keep this monitor anyway, even if you don't fix it. You never know when you might find another monitor that may need just a part or two from this monitor (like the CCFL backlights, inverter transformers, etc.).

Either way, I don't mind helping you at all. So it's up to you what you want to do at this point. If you want to continue, let me know.

[rigeback]

Re: Monitor problems

I checked U-4 out and its just a mark, maybe I touched it with a felt tip marker, I cleaned off with a some alcohol.
You're right I'm just doing this as a hobby and to learn a bit about electronics, if all fails I keep it for parts and knowing whats wrong with it could come in useful later on.

[rigeback]

Re: Monitor problems

Sorry I forgot to metion part number on U-1 = AEK642.
By the way I would prefer to get this monitor repaired as it saves space and the visual is good! I have found a supplier here in Italy for the fuses and hopefully this week I will be ready fit the K fuse.

[momaka]

Re: Monitor problems

I have found a supplier here in Italy for the fuses and hopefully this week I will be ready fit the K fuse.

Sounds good, just make sure to get at least a 2 or 3 of those fuses, in case the first one decides to blow or you happen to loose one. If you end up not being able to find a proper sized fuse, just grab one that is close enough in size (still needs to have the same current rating of 1.5 Amps, though).

As far as U1, again I'm unable to find a datasheet.
But while waiting to get the fuse, I would like you to measure one more resistance (again, manual multimeter, 2k scale): measure resistance between VCC1 (middle pin of U1) and left pad of fuse F1. This will tell if U1 is shorted or not. Let me know what measurements you get.

[rigeback]

Re: Monitor problems

Strange readings when I measured resistance between VCC1 (middle pin of U1) at first it held at .022 and then 0.06 and last test it gives 0.00
U1 - K fuse holds at ,522 @2K and 67,2 @200K
I found some 1.5V ceramic fuses on an uld hard drive although they are a bit longer, not sure they fit.

[momaka]

Re: Monitor problems

Try the auto multimeter then. See if you get the same results.

[rigeback]

Re: Monitor problems

Yes its the same with the auto meter starts off with a few numbers and in no time drops to 0.00 do think this the problem part?
I've got a router thats corrupted and it has one of these LDO chips, I took some readings of the router LDO and the values differ, athough if this one is damaged the values would not be much use to work with?

[momaka]

Re: Monitor problems

Yes its the same with the auto meter starts off with a few numbers and in no time drops to 0.00 do think this the problem part?

Well, if the multimeter really is showing zero Ohms and this is not changing when you reverse the probes, then you truly do have a short circuit between VCC1 and 5v supply (5v supply is the rail connected to fuse F1). This means that U1 is shorted. This could be quite bad, but we will see...

Check the resistance of resistors R9 and R85. To do this, see what value is printed on them, then measure resistance across each. If the measured resistance is the same (or 5% higher) or much lower than the stated value on the case of each resistor, then that resistor is good. Alternatively, if the measured reading is much higher than what is printed on the case of those resistors, then they might need to be replaced as well.
If you're not sure what I mean, just posts the numbers written on R9 and R85, and also their measurements.

By the way, how are your soldering skills?

[rigeback]

Re: Monitor problems

Both R=9 & R-85 @ 2k gave 0.00 readings, I couldn't see the numbers with a magnifier but my daughter says that both chips were marked with 000, is this possible? Contiuity is there.
Tomorrow I will try with another camera to get a real close up.
I can solder but its my vision thats impaired!

[rigeback]

Re: Monitor problems

Yes my daughter is right the 2 chips are markes with 3 zero's 000! I used a double magnifier glass.

[retiredcaps]

Re: Monitor problems

2 chips are markes with 3 zero's 000!

I believe 000 means it is a 0 ohm resistor. A jumper in other words.

I see these on some of my boards, but it typically only has a single 0 instead of 000.

[momaka]

Re: Monitor problems

Both R=9 & R-85 @ 2k gave 0.00 readings, I couldn't see the numbers with a magnifier but my daughter says that both chips were marked with 000, is this possible?

Yes, sir.
Your measurements indicate that R9 and R58 are good.
Unfortunately, however, this means that U1 will have to be removed from the board and tested out of circuit. Test U1 just like you did before - i.e. measure resistance between middle and top pins on the right side of U1. If it's still showing 0 Ohms out of circuit, then U1 is bad.

Either do that, or alternatively, you can remove R9 and R58 and then test U1. From what I can see from your picture of the t-con, VCC1 is not connected to anything else other than R9 and R58. Perhaps C18 (the small ceramic capacitor to the right of test point VCC1). I guess it would be a good idea to see what C18 is connected to. The left pin of C18 is obviously connected to VCC1, but the right pin could be connected to ground or it could be connected to the 5v rail. See which one it is by performing a continuity check with your multimeter between ground and right pin of C18 and then 5v rail and right pin of C18.

If right pin of C18 is connected to 5v rail, remove C18. Otherwise, you'll have to do what I mentioned above - that is, either remove U1 and check it out of circuit, or remove R9 and R58 and then check U1 without removing it. Do whichever you're more comfortable with, because surface mounted components are a pain to remove (and put back).

Before doing all of that though, I still think it would be best to get that "K" type fuse replaced first, then test the monitor with everything connected normally. If the monitor doesn't work, then proceed with removing U1/ R9 and R58. I always test things a few times before finally resorting to component removal.

[rigeback]

Re: Monitor problems

After removing the K fuse I did a test for contenuity on C-18 and it is connected to ground and the center pin of U-1, it does not seem connected to the 5v rail.
I could not replce the fuse as its a bit longer, is it possible to solder a jumper wire to the fuse from the board to carry out the test?
I am still waiting to hear from a company here about a new fuse.

[PlainBill]

Re: Monitor problems

After removing the K fuse I did a test for contenuity on C-18 and it is connected to ground and the center pin of U-1, it does not seem connected to the 5v rail.
I could not replce the fuse as its a bit longer, is it possible to solder a jumper wire to the fuse from the board to carry out the test?
I am still waiting to hear from a company here about a new fuse.

Yes.

PlainBill

[rigeback]

Re: Monitor problems

Guys, I'm writing on that monitor, shes been working for 2 days now and with a great picture. I'm not sure if we should close the topic just yet though? Anyway I'm real pleased with out come so far with thanks to ya'all.

[momaka]

Re: Monitor problems

Congratulations!

So you just changed the "K" type fuse and it worked?
If so, I think you are only the second person I see this happen to.
Very interesting.
Nice work.

[rigeback]

Re: Monitor problems

Well not exactly as the fuse is detached from the t-con board with wires as I could find a fuse that size, but it works and I'm real pleased.